The effect of propylene glycol (PG) on transdermal flux under current was investigated using conventional in vitro iontophoresis methodology. The results were evaluated to explain how PG affects the electroosmotic volume flow (EVF) and electromigrational flux through skin. As a marker molecule for the direction and magnitude of EVF, a non-charged neutral molecule, acetaminophen (AAP), was used. At pH 7.4, the direction of EVF was from anode to cathode. During anodal and cathodal current application, PG decreased AAP flux and this decrease was proportional to the concentration of PG, indicating that the presence of PG in the medium decreased the EVF. This decrease is likely due to the decrease in dielectric constant of the medium and the increases in medium viscosity by the addition of PG. The increase in AAP solubility and the viscosity of the medium by PG may also contribute to the decrease in diffusional flux. The magnitude of EVF was estimated to be about 4.2 μl/cm(2 )h. The effect of PG on the flux of a positively charged drug, donepezil hydrochloride (DH), was further investigated using pH 4.6 phosphate buffer solution. The permselectivity of skin in this solution was also investigated and revealed that the isoelectric point of hairless mouse skin is higher than pH 4.6. Anodal delivery showed much higher flux than cathodal and passive flux, indicating that electromigration is playing the major role for DH flux. As the concentration of PG increased, anodal flux of DH decreased. The main reason for this decrease in electromigration is likely due to the increase in medium viscosity. These results and discussions clearly suggest that the incorporation of frequently used organic cosolvents and penetration enhancers into the iontophoretic formulation should be carefully chosen with a thorough investigation for their effect on flux. Overall, these results provided further mechanistic insights into the role of electroosmosis and electromigration in flux across skin, and how they can be modulated by organic cosolvent, PG.

译文

使用常规的体外离子电渗法研究了丙二醇 (PG) 对电流下透皮通量的影响。对结果进行了评估,以解释PG如何影响通过皮肤的电渗体积流量 (EVF) 和电迁移通量。作为EVF方向和大小的标记分子,使用了不带电的中性分子对乙酰氨基酚 (AAP)。在pH 7.4时,EVF的方向是从阳极到阴极。在阳极和阴极电流施加期间,PG降低了AAP通量,并且这种降低与PG的浓度成正比,表明培养基中PG的存在降低了EVF。这种降低可能是由于介质的介电常数降低和通过添加PG而增加介质粘度。PG增加AAP溶解度和介质粘度也可能导致扩散通量的降低。估计EVF的大小约为4.2 μ l/cm(2 )h。使用pH 4.6磷酸盐缓冲溶液进一步研究了PG对带正电的药物盐酸多奈哌齐 (DH) 的通量的影响。还研究了该溶液中皮肤的渗透选择性,并发现无毛小鼠皮肤的等电点高于pH 4.6。阳极递送显示出比阴极和被动通量高得多的通量,表明电迁移在DH通量中起主要作用。随着PG浓度的增加,DH的阳极通量降低。电迁移减少的主要原因可能是由于介质粘度的增加。这些结果和讨论清楚地表明,应仔细选择将常用的有机助溶剂和渗透增强剂掺入离子电渗制剂中,并仔细研究其对通量的影响。总体而言,这些结果为电渗和电迁移在整个皮肤通量中的作用以及如何通过有机助溶剂PG调节它们提供了进一步的机械见解。

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